Instrument for gravimetric moisture determination with temperature sensor

ABSTRACT

An instrument ( 10 ) for gravimetrically determining moisture content has a housing ( 20 ), with a weighing device ( 40 ) arranged inside. The weighing device ( 40 ) has a load receiver ( 60 ) onto which a sample ( 62 ) is placed. The housing has a lower, stationary housing part ( 21 ) and an upper, movable housing part ( 22 ), the movable housing part alternately occupying a measuring position and a loading position. In the loading position, the respective housing parts are spaced apart from each other, allowing a sample to be put on the load receiver. In the measuring position, the respective housing parts form an essentially enclosed testing compartment ( 30 ) that surrounds the load receiver. A temperature sensor ( 80 ) is arranged so that the temperature sensor is above the load receiver in the measuring position and is essentially to the side of the load receiver in the loading position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to benefit of a right of priority under 35USC §119 from European patent application 11183600.3, filed 30 Sep.2011, the content of which is incorporated by reference as if fullyrecited herein.

TECHNICAL FIELD

The disclosed embodiments relate to a measuring instrument for thegravimetric determination of moisture content, particularly aninstrument in which a temperature sensor is included.

BACKGROUND

The moisture content of a sample is determined by drying the sample andby manually determining its weight before and after the drying process.Due to the laborious procedures involved, this method is very expensiveand error-prone.

Under certain conditions, the weight loss can also be determined duringthe drying process. For a given sample, the measured value for theweight decreases as a function of the temperature, the elapsed dryingtime, and the parameters of the testing compartment, according to aweight/time graph which asymptotically approaches the dry weight of thesample. Based on the available electronic capabilities, an appropriatelyequipped measuring instrument for the gravimetric determination ofmoisture content is able to calculate the moisture content of a samplefrom the measured parameters of the graph and the drying time and toindicate the moisture content on a display unit. With this method, it isno longer necessary for the material under test to be completely driedout, because sufficient information is obtained by determining thecoordinates of two measurement points in the weight/time diagram.

As mentioned above, the change in the weight of a sample is essentiallya function of the temperature, the elapsed drying time, and theparameters of the testing compartment. The instruments that arecommercially available at this time are limited in their accuracyprimarily because of the demanding requirements which have to be met bythe testing compartment.

Normally, the sample is spread in a thin layer onto a flat samplereceiver, for example a sample tray. The tray is arranged inside thegravimetric moisture determination instrument, extending preferably in ahorizontal plane and parallel to the plane of the sample-heating means,in order to achieve a uniform heating of the sample.

Devices that are used as sample-heating means include a variety ofradiation sources such as radiant heaters, microwave generators,halogen- and quartz lamps. As could be established by experiments, oneof the main causes for the inaccuracy in the determination ofmeasurement values in existing gravimetric moisture-determinationinstruments lies in the nature of the radiation sources being used andin their arrangement in the testing compartment.

A measuring instrument of the aforementioned kind for the gravimetricdetermination of moisture content is described in the European Patent EP0 611 956 B1. In this instrument, the loading of the weighing pan occursoutside of the gravimetric moisture-determination instrument. To loadand unload the sample, the balance which is arranged on a drawer-likecarriage is slid out of the instrument housing. As a radiation source, aring-shaped halogen lamp is being used which, in the operating state ofthe apparatus, is arranged above the sample receiver. Examples offurther design configurations are published in EP 1 850 110 A1. Forexample, a measuring instrument is disclosed which is opened up forloading through a horizontal swivel movement of a part of the housing.In a further embodiment, a part of the housing is swiveled in thevertical direction. Likewise, the measuring instruments disclosed inU.S. Pat. No. 7,851,712 B2 are opened for loading by verticallyswiveling a part of the housing.

Some of these types of designs have the disadvantage that theirradiation sources, hereinafter also referred to as sample-heating means,are openly exposed during the loading process. After the measurementshave been completed, these radiation sources and/or oven walls are hotand pose a risk of injury to the user.

It is therefore an object to provide a measuring instrument forgravimetric moisture determination which offers the assurance of usersafety.

SUMMARY

This task is solved by the measuring instrument for gravimetric moisturedetermination in accordance with the appended claims.

The measuring instrument for gravimetric moisture determinationcomprises a housing and a weighing device arranged inside the housing,wherein the weighing device has a load receiver onto which a sample canbe placed. The housing has a lower, stationary housing part and anupper, movable housing part. The movable housing part can occupypositions for measuring and for loading, respectively, wherein in theloading position, the stationary housing part and the movable housingpart are spaced apart from each other in such a way that a sample can beput on the load receiver. In the measuring position, the stationaryhousing part and the movable housing part form an essentially enclosedtesting compartment around the load receiver. Arranged in the testingcompartment is a means for the heating of a sample that is placed on theload receiver. A temperature sensor is arranged so that in the measuringposition the temperature sensor occupies a place above the load receiverand in the loading position its place is essentially to the side of theload receiver. With this arrangement, an accurate temperature value canbe determined for the sample when the instrument is in measuringposition. With the instrument in loading position, the temperaturesensor is out of the way of the user putting the sample in place.

The term “housing part” in the present context is meant to include theelements of the instrument that are attached to it. Typically, thesample-heating means is arranged in the movable housing part while theweighing device, the sample receiver and the electronic module arearranged in the stationary housing part.

The term “testing compartment” means a space which is enclosed by thehousing of the measuring instrument and which can be opened and closedin order to bring in or take out a sample. Arranged inside the testingcompartment are a sample receiver and a means for heating the sample.The sample receiver is connected to a gravimetric measuring instrument.

Preferably, the temperature sensor is designed to move upwards and tothe side with the change from the measuring position to the loadingposition. Ideally, this lateral and upward movement of the temperaturesensor is directed away from the user, giving free access to the samplereceiver.

Ideally, the temperature sensor is arranged on a rod that is attached tothe stationary housing part. Thus, the temperature sensor and the rodare not participating in a position change of the movable housing part.

Preferably, the rod is attached to the stationary housing part by meansof a fulcrum pivot. Ideally, the axis of the fulcrum pivot isessentially horizontal. In the shift from the measuring position to theloading position, this arrangement allows the rod with the temperaturesensor to be moved in a circular arc, simultaneously upward andlaterally away from the sample receiver. Alternatively, a purely lateralmovement would also be conceivable.

Different mechanisms can be used to move the rod from the measuringposition to the loading position. In one possible configuration, the rodis pre-tensioned in the measuring position by means of a spring element,so that the rod can be moved from the measuring position to the loadingposition by the elastic force of the spring element. In the measuringposition, the spring element is preferably held under tension by themovable housing part. When the movable housing part is brought from themeasuring position to the loading position, the rod with the temperaturesensor will also move automatically from the measuring position to theloading position.

In the measurement position, the temperature sensor is ideally locatedbetween the sample-heating means and the load receiver, with thesample-heating means being arranged in the movable housing part. Withthis arrangement, the temperature sensor is located close to the sampleand the temperature of the sample is determined with the highestpossible accuracy.

Preferably, only the stationary housing part is connected to line power,and the temperature sensor can be supplied with electricity from thestationary housing part. This arrangement has the advantage that thepower supply connection of the temperature sensor does not need to runthrough the movable housing part. While the movable housing part is notsupplied with current in the loading position, the temperature sensor,being mounted on the stationary housing part, continues to receive powerand can be used, for example, for the measurement of the ambientconditions.

Ideally, the measuring instrument includes an electrical contact meanswith a first part and a second part. The first part of the electricalcontact means is connected to the stationary housing part, and thesecond part of the electrical contact means is connected to the movablehousing part. In the measurement position, an electrical connectionexists by way of the first and the second part of the electrical contactmeans. In the loading position, the electrical connection between thefirst and the second part of the electrical contact means isinterrupted. Furthermore, if the movable housing part is supplied withelectricity only by way of the electrical contact means, no voltage isapplied to the movable housing part during the loading phase. Thetemperature sensor, being fastened to the stationary housing part, issupplied with electricity also in the loading position. This means thatthe temperature sensor can also be used to measure the temperatureduring loading. It is possible, for example, to measure the ambienttemperature during the loading phase.

In a preferred embodiment, the movable housing part can be brought in atranslatory movement from the measuring position to the loading positionwith the help of a position-changing means. With this movement theelectrical contact between the first and the second part of theelectrical contact means and/or of the electronic contact means can beinterrupted.

The electrical contact means and/or the electronic contact means areadvantageously configured as a plug-in connection, i.e. a connectionbetween a plug and a socket. The insertion of the plug into the socketcan occur in an essentially vertical direction. A pivotable, concentricplug connection of the kind used in water heaters has provenparticularly suitable as electrical contact means. The pivotable,concentric plug connection is particularly robust and reliable inclosing and opening an electrical contact.

Preferably, the movable housing part is movable simultaneously in thehorizontal and in the vertical direction. The movement, morespecifically the translatory displacement, of the movable housing partcan take place as a parallel displacement. This displacement shifts themovable housing part simultaneously in the upward direction and to therear, i.e. away from the user. Ideally, the movable housing part isattached to the stationary housing part by way of position-changingelements. When the movable housing part is moved from the loadingposition to the measuring position, the movement has the result ofconnecting the electrical contact means to each other.

In a preferred embodiment, the movable housing part is located above thestationary housing part, both in the measurement position and in theloading position of the apparatus. This can be realized with aconfiguration where the movable housing part is significantly shorterthan the stationary housing part in the direction of horizontalmovement. Ideally, the length of the movable housing part is less thanhalf the length of the stationary housing part. The position-changingmeans is designed so that when the movable housing part is moved, it isalways at a location above the stationary housing part.

In a preferred embodiment, the movable housing part can be brought fromthe measurement position to the loading position with the help of aposition-changing means.

Preferably, the movable housing part is movable simultaneously in thehorizontal and in the vertical direction. The movement, morespecifically the translatory position change, of the movable housingpart can take place as a parallel displacement. This displacement shiftsthe movable housing part simultaneously in the upward direction and tothe rear, i.e. away from the user. Ideally, the movable housing part isattached to the stationary housing part through position-changingelements.

In a preferred embodiment, the movable housing part is located above thestationary housing part, both in the measurement position and in theloading position of the apparatus. This can be realized with aconfiguration where the movable housing part is significantly shorterthan the stationary housing part in the direction of horizontalmovement. Ideally, the length of the movable housing part is less thanhalf the length of the stationary housing part. The position-changingmeans is designed so that when the movable housing part is moved, it isalways at a location above the stationary housing part.

Ideally, the heating means is arranged in the movable housing part insuch a way that in the measuring position the sample-heating means islocated above the sample receiver, and in the loading position thesample-heating means is located above the stationary housing part. Thishas the advantage that the sample can be heated from above. As thesample-heating means is arranged on top, it is less susceptible tocollecting dirt.

The heating means is designed so that it can be swiveled together withthe movable housing part from the measuring position into the loadingposition. This has the essential advantage that it reduces the danger ofinjury, because neither in the measuring position nor in the loadingposition can the heating means be inadvertently touched by the user.

Ideally, the arrangement of the sample-heating means in the movablehousing part is such that in measuring position the sample-heating meansis located above the sample receiver, and in loading position thesample-heating means is located above the stationary housing part. Asthe heating means is arranged on top, it will be less likely to collectdirt.

Ideally, the heating means in the measurement position and/or loadingposition extends in essence in a horizontal plane above the samplereceiver.

For the purpose of servicing, at least a portion of the movable housingpart can be pivoted from the loading position into a service positionabout an essentially horizontal tilt axis. The tiltable portion of themovable housing part contains the heating means which, in the servicingposition, is thus made accessible to a service technician for thepurpose servicing. In the servicing position, the heating means is inessence oriented in a vertical position and facing the user. With thisarrangement, the heating means is easily accessible and can be servicedin a simple manner. The position of the temperature sensor in theservicing position is the same as in the loading position.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the measuring instrument may be learned from the descriptionof the embodiment illustrated in the drawings, wherein:

FIG. 1, in a sectional view, shows a schematic representation of ameasuring instrument in measuring position;

FIG. 2, in a sectional view, shows a schematic representation of themeasuring instrument of FIG. 1 in loading position;

FIG. 3 a shows a schematic representation of a further measuringinstrument with a temperature sensor, wherein the latter is in measuringposition;

FIG. 3 b shows a schematic representation of the measuring instrument ofFIG. 3 a, wherein the temperature sensor is in the loading position;

FIG. 4 shows an isometric representation of the measuring instrument inmeasuring position;

FIG. 5 shows the measuring instrument of FIG. 4 in loading position;

FIG. 6 shows the measuring instrument of FIG. 4 in servicing position;

FIG. 7 shows the measuring instrument of FIG. 6 in servicing positionwith partially removed glass shield and draft protector; and

FIG. 8 shows the movable housing part of the measuring instrument ofFIG. 7 in servicing position without glass shield.

DETAILED DESCRIPTION

FIGS. 1 and 2 represent schematic, sectional views of a measuringinstrument 10 in measuring position (FIG. 1) and in loading position(FIG. 2). The measuring instrument 10 has a housing 20 in which atesting compartment 30 is arranged. The housing 20 is subdivided into amovable housing part 22 and a stationary housing part 21. When theinstrument is in use, the stationary housing part 21 is standing on asolid support surface. The movable housing part 22 is attached to thestationary housing part. To the rear, i.e. on the side of the testingcompartment 30 that faces away from the user, a weighing device 40 isarranged in the stationary housing part 21. The movable housing part 22is constrained on the stationary housing part 22 by means of atranslatory-motion guide 24. The translatory-motion guide 24 isconfigured so that the movable housing part 22 maintains an essentiallyconstant orientation during its movement from the measuring positioninto the loading position. In other words, during its movement themovable housing part 22 remains essentially parallel to the stationaryhousing part 21. The stationary housing part 21, which is configured asa hollow body, contains a weighing cell 43 and at least one electronicmodule 90 which are connected to each other by transfer means 52. Theelectronic module 90 includes at least one signal-processing module (notshown in detail) and in some cases also a controller- and/or regulatormodule. The weighing cell 43 has at least one stationary portion 41 anda load-receiving portion 42. State-of-the-art types of weighing cellsinclude for example elastic deformation bodies carrying strain gauges,weighing cells that operate according to the principle ofelectromagnetic force compensation, weighing cells with oscillatingstrings, capacitative weighing sensors and the like. The stationaryportion 41 of the weighing cell 43 is solidly connected to thestationary housing part 21. Arranged on the load-receiving portion 42 isa connecting member 47 through which a sample receiver 60 is connectedto the load receiving portion 42 of the weighing cell 43. As shown inthe drawing, a sample tray 61 with a sample 62 can be set on the samplereceiver 60. If the sample receiver 60 is suitably configured, thesample 62 can of course also be put directly on the sample receiver 60.

The measuring instrument 10 as shown in FIG. 1 is in measuring positionwhich means that the sample receiver 60 and the sample tray 61 sittingon it are inside the testing compartment 30. The stationary housing part21 and the movable housing part 22 form an essentially enclosed testingcompartment 30 surrounding the sample receiver 60. A heating means 70 isarranged essentially parallel to the plane of the sample receiver 60, soas to obtain as homogeneous a heat distribution as possible at least onthe surface of the sample 62. It is also possible to arrange anadditional heating means in the testing compartment 30 below the samplereceiver 60 in order to expose the underside of the sample 62 toradiation. However, it is not absolutely necessary to arrange theheating means 70 parallel to the plane of the sample receiver 60.Depending on the sample 62 and on the measurement that is to beperformed, it may also be advantageous to arrange the heating means 70at an oblique angle to the sample receiver 60.

To allow the moisture given off by the sample 62 to escape from thetesting department 30, the housing 20 has outlet vents 27 arranged at anappropriate location of the movable housing part 22, preferably abovethe heating means 70. To generate sufficient air circulation inside thetesting compartment 30, there should further be air vent openingsprovided at appropriate locations.

The measuring instrument 10 in FIG. 1 is shown in measuring position.The stationary housing part 21 and the movable housing part 22 form anessentially enclosed testing compartment 30. The latter is essentiallydelimited at the top by the movable housing part 22 and at the bottom bythe stationary housing part 21. The heating means 70 is arranged in themovable housing part 22. Ideally, the heating means 70 is mechanicallyconnected to the movable housing part 22 through releasable plug-inconnections. Thus, the heating means 70 can be uninstalled without mucheffort for cleaning or repair. Furthermore, with the use of plug-inconnections the user of the measuring instrument 10 is able to selectfrom different heating means with different functional characteristics.This enables the user to match the conditions inside the testingcompartment to a specific sample 62.

The measuring instrument 10 includes an electronic module 90 which isarranged in the stationary housing part 21. The electronic module 90 hasa variety of controller/regulator devices. Among others, the electronicmodule 90 also includes a controller/regulator device for the controland regulation of the heating means 70. A temperature sensor 80 which isillustrated schematically in the drawing serves to measure thetemperature of the sample 62 and to deliver to the controller/regulatordevice 35 the information required for the regulation of the heatingmeans 70. The controller/regulator device 35 is further connected to theweighing device 40, specifically to the electronic module 90, by meansof at least one transfer means 52. The transfer means 52 serves for thetransmission of electrical and/or electronic signals. As a result, thecontroller/regulator device 35 can receive signals from the electronicmodule 90. The measuring instrument 10 is supplied with power by meansof an electrical connection 88. The electrical power connection 88 isarranged on the stationary housing part 21. Preferably, the electricalcurrent is delivered only by way of the stationary housing part 21.Thus, the user or the service technician is not subjected to the risk ofreceiving an electric shock in the course of a servicing operation.

The controller/regulator device 35 and the temperature sensor 80 areconnected to each other through a transfer means 51. Furthermore, thecontroller/regulator device 35 and the sample-heating means 70 areconnected to each other through a further transfer means 53. Thetransfer means 51, 53 serve to transmit electrical and electronicsignals between the respective apparatus components. During themeasurement process, the temperature in the testing compartment 30 ismeasured by means of the temperature sensor 80. The temperature signalgenerated by means of the temperature sensor 80 is transmitted by way ofthe transfer means 51 to the controller/regulator device 35. For thecontroller/regulator device 35 the temperature signal is an input signalbased on which the sample-heating means 70 is controlled. In themeasurement position, the temperature sensor 80 is located between thesample receiver 60 and the sample-heating means 70. This arrangementmakes it possible to obtain the temperature value that is relevant forthe measurement. The temperature sensor could also be placed at adifferent location. However, the temperature values that are therebyobtained are less accurate in representing the heat level in the testingcompartment. The temperature sensor 80 is arranged on a rod 81 which isfastened to the stationary housing part 21. The rod 81 is essentiallyrigid, with a first end and a second end. Arranged at the first end isthe temperature sensor 80, while the second end is connected to thestationary housing part 21. Due to the fact that the second end isconnected to the stationary housing part 21, the operation of thetemperature sensor 80 does not require an electrical and/or electronicconnection from the stationary housing part 21 to the movable housingpart 22.

The transfer means 51 is arranged at or inside the rod 81. The rod 81can be swivel on a fulcrum pivot 82. The fulcrum pivot 82 is at thesecond end of the rod 81 and has a substantially horizontal pivot axis83.

The rod 81 and the fulcrum pivot 83 are arranged so that during thechange from the measuring position to the loading position, thetemperature sensor 80 moves along a circular path in a vertical plane.Arrangements are also possible where the circular path lies in adifferent, i.e. non-vertical plane. For example, the axis of the fulcrumpivot can be given an essentially vertical orientation, so that thetemperature sensor 80 is constrained to a circular path in a horizontalplane during the change from the measuring position to the loadingposition.

In the measuring position, the rod 81 is force-biased by the springtension of a spring element 84. When the movable housing part 22 isbrought from the measuring position into the loading position, the rod81 moves away from the sample receiver 60 under the elastic force of thepre-tensioned spring element 84. In the loading position, thetemperature sensor 80 and the rod 81 are therefore not obstructing theaccess to the sample receiver 60, which facilitates the loading of themeasuring instrument. Ideally, the spring element 84 is constituted by atorsion spring wherein the torque axis coincides with the axis of thefulcrum pivot 83. Of course, other spring elements could also be used,such as for example compression spring elements. In any case, the springelement needs to be arranged so that it is elastically biased in themeasuring position while being unstressed or less biased in the loadingposition.

As the sample-heating means 70 is arranged in the movable housing part22 and the controller- and regulator device 35 is arranged in thestationary housing part 21, the transfer means 53 has to transmitelectrical and/or electronic signals from the stationary housing part 22to the movable housing part 21. This can be accomplished for examplewith a flexible cable. However, due to the position shifts of themovable housing part 21, this cable would be subjected to bending cyclesand therefore susceptible to wear.

This problem can be circumvented by using an electrical contact meanswith a first part 86 and a second part 87, wherein the first part 86 isconnected to the movable housing part 22 and the second part 87 isconnected to the stationary housing part 21. Under this concept, thefirst and the second part of the electrical contact means 86, 87 arearranged so that in the measuring position the first and second part 86,87 form an electrical connection, and that in the loading position theelectrical connection is interrupted. It is a significant advantage ofthis arrangement that in the loading position the sample-heating means70 is not supplied with electricity. Ideally, the electronics for thecontrol are arranged exclusively in the stationary housing part 22. Thecontrol of the sample-heating means 70 takes place only by way of thefirst and second electrical contact means 86, 87. Therefore, noconnection is needed for the transmission of control signals to themovable housing part 21. This is a further reason for arranging thetemperature sensor 80 on the stationary housing part 21. If thetemperature sensor 80 were arranged on the movable housing part 22, itwould be necessary to transmit signals between the stationary housingpart 21 and the movable housing part 22. As a further advantage of themeasuring instrument 10, the temperature can also be measured andregistered in the loading position by means of the temperature sensor80. Thus, it is for example possible to measure the ambient temperatureduring the loading process.

The electrical contact means 86, 87 include a plug-in connection whereone of the two parts of the electrical contact means 86 is configured asa plug and the other part as a socket that cooperates with the plug. Thedirection of insertion of the plug connection is essentially vertical.

In FIG. 2 the measuring instrument 10 of FIG. 1 is shown in loadingposition. By means of a translatory-motion guide 24, the movable housingpart 22 can be moved away from the stationary housing part 21, wherebythe measuring instrument 10 is brought from the measuring position intothe loading position. In this change of position, the movable housingpart 22 undergoes in essence a purely translatory displacement. In theloading position the movable housing part 22 is located above thestationary housing part 21 and above the weighing device 40. Thesample-heating means 70 in this position is located between the movablehousing part 22 and the stationary housing part 21. This preventsaccidental touching of the sample-heating means 70 which may be veryhot.

In the change to the loading position, the temperature sensor 80 ismoved upward and laterally away from the sample receiver 60. Thus, thetemperature sensor 80 will not interfere with the loading of the samplereceiver 60.

In the loading position, the electrical contact means 86, 87 isinterrupted. There is no electricity flowing from the stationary housingpart 21 to the movable housing part 22. Since the movable housing part22 does not have a power connection of its own, no electric current isentering the movable housing part 22 in the loading position.

FIGS. 3 a and 3 b illustrate a further measuring instrument 110 in aschematic representation. FIG. 3 a shows the measuring instrument 110 inthe measuring position, and FIG. 3 b shows the same measuring instrument110 in the loading position.

The measuring instrument 110 has a housing 120 with a stationary housingpart 121 and a movable housing part 122.

When the instrument is in measuring position, the stationary housingpart 121 and the movable housing part 122 together form an essentiallyenclosed testing compartment 130, in which the sample receiver 160 islocated. Arranged above the sample receiver 160 is a sample-heatingmeans 170. The sample-heating means 170 is solidly connected to themovable housing part 122. A temperature sensor 180 is arranged on a rod181. The rod 181 has a first and a second end. Attached to the first endis the temperature sensor 180, while the second end is pivotallyconnected to the stationary housing part 121. In the measuring positionof the instrument, the temperature sensor 180 is located above the loadreceiver 160 and underneath the sample-heating means 170. In loadingposition, the temperature sensor 180 is located essentially off to theside of the load receiver 160. This is accomplished with a design wherethe rod 181 is rigid and is connected to the stationary housing part 121by means of a fulcrum pivot 182. Ideally, the axis 183 of the fulcrumpivot 182 is oriented horizontally. In measuring position, the rod 181can be spring-biased by the elastic force of a spring element. When themovable part 122 is moved from the measuring position into the loadingposition, the rod 181 moves upwards and laterally in a circular arcunder the biasing force of the spring element. In the measurementposition, the spring element is preferably held in a pre-tensioned stateby the movable housing part 122.

To obtain the most stable measurement results possible, there can be aninterior draft shield arranged inside the testing compartment (see FIGS.6-8). This interior draft shield is arranged so that it surrounds thesample receiver 160 and the sample-heating means 170, delimiting anearly enclosed section of space. The interior draft shield can includean upper part 174 and a lower part 165. The upper part 174 is arrangedon the movable housing part 122. The upper part 174 of the interiordraft shield forms a cylindrical interior space which is open towardsthe sample receiver. Arranged inside this cylindrical interior space isthe sample-heating means. The upper part of the interior draft shieldcan consist of a cylindrical circumference wall alone. However, it isadvantageous if the cylinder has an upper end wall which is horizontallyoriented in the measuring and in the loading position of the instrument.This end wall is preferably arranged above the sample-heating means 170.Ideally, the side of the end wall that faces towards the sample-heatingmeans 170 is heat-reflecting. Consequently, a part of the heat that isbeing generated is reflected by the interior draft shield and used toheat the sample which is located on the sample receiver 160. The lowerpart 165 of the interior draft shield is arranged on the stationaryhousing part 121. The lower part 165 of the interior draft shield formsa cylindrical interior space which is open towards the sample-heatingmeans 170. Arranged in this cylindrical interior space is the samplereceiver 160. In measuring position, the interior space of the upperpart 174 of the interior draft shield and the interior space of thelower part 165 of the interior draft shield form a chamber in which thesample-heating means 170 and the sample receiver 160 are located. Theupper as well as the lower part of the interior draft shield 165, 174can be made of one piece of material or assembled from several sections.

FIGS. 4, 5, 6, 7 and 8 illustrate an embodiment of the measuringinstrument 210 in different positions. The measuring instrument 210 hasall of the components that have already been covered in the descriptionof the schematic drawings of FIGS. 1 and 2.

FIG. 4 shows the measuring instrument 210 in measuring position. As thehousing 220 is closed in the measuring position, most of the componentscannot be seen. The housing 220 has a stationary housing part 221 and amovable housing part 222. In measuring position, the stationary housingpart 221 and the movable housing part 222 form an essentially enclosedtesting compartment. The movable housing part 222 has outlet ventopenings 227 which allow gases to escape from the testing compartmentinside the housing 220 into the ambient atmosphere. Advantageously, inthe measurement position of the instrument the outlet vent openings 227are located on the topside of the movable housing part 222. Especiallyadvantageous is an arrangement of the outlet vent openings 227 above thesample-heating means 170 which is likewise arranged inside the housing220.

FIG. 5 shows the measuring instrument 210 of FIG. 4 in loading position.The movable housing part 222 has been brought from the measuringposition into the loading position by a translatory movement. To enablethis translatory movement, the movable housing part 222 is connected tothe stationary housing part 221 by a translatory-motion guide 224. Thetranslatory-motion guide 224 has two essentially parallel pivoting legswhose orientation defines the direction of the translatory movement ofthe movable housing part 222.

The stationary housing part 221 is of an elongated shape. The weighingdevice is largely enclosed by the stationary housing part 221. Only asample receiver 260 which is connected to the weighing device protrudeslaterally from the stationary housing part 221. Containers of variousshapes such as sample trays, crucibles and the like can be put on thesample receiver 260. The stationary housing part 221 includes a portionthat is located to the side of the sample receiver 260 that faces awayfrom the user. Advantageously, in this portion the weighing device isarranged. In loading position, the movable housing part 222 is locatedabove the stationary housing part 221, ideally above the portion that islocated to the side of the sample receiver 260.

The movable temperature sensor 280 is arranged on a pivotally mountedrod 281. As described in the schematic representation of FIGS. 3 a and 3b, the rod 281 is connected to the stationary housing part by means of afulcrum pivot. The axis of the fulcrum pivot is likewise orientedhorizontally, and the rod 281 is likewise elastically biased in themeasuring position by means of a spring force. In the measuringposition, the temperature sensor 280 is located between thesample-heating means 270 and the sample receiver 260. In the loadingposition, the temperature sensor 280 and the rod 281 are removedsideways and upward from the sample receiver 260. This makes it possibleto load a sample on the measuring instrument 210 without the temperaturesensor 280 standing in the way of the user.

The sample-heating means 270 is arranged in the movable housing part222. During the measurement, the sample-heating means 270 becomes hotand thereby heats the sample which is arranged below the heating meanson the sample receiver 260. An electric current is required for theheating. The stationary housing part 221 is therefore equipped with apower connector 288 which is arranged on the backside of the measuringinstrument 210. The movable housing part does not have a powerconnection of its own. The electric current therefore has to betransmitted from the stationary housing part 221 to the movable housingpart 222. This is accomplished with an electrical contact means whichhas a first part 286 and a second part 287. The first part 286 of theelectrical contact means is connected to the movable housing part 222,while the second part of the electrical contact means is connected tothe stationary housing part 221. The two parts 286, 287 of theelectrical contact means are arranged so that in measuring position anelectrical contact exists from one to the other and the sample-heatingmeans 270 is supplied with electrical current. In the loading position,there is no contact through the electrical contact means 286, 287. Theelectrical contact is established automatically by the movement of themovable housing part 222. A pivotable, concentric plug connection of thekind used in water heaters has proven particularly suitable aselectrical contact means. The pivotable, concentric plug connection isparticularly robust and reliable in closing and opening an electricalcontact. However, other configurations are likewise conceivable.Particularly suitable are plug/socket connections.

With this arrangement, an electrical connection exists in the measuringposition by way of the first and second part of the electrical contactmeans 286, 287, while the connection between the first and second partof the electrical contact means 286, 287 is interrupted in the loadingposition. In the loading position, the heating means is therefore notunder power and the risk of injury is therefore reduced. The second partof the electrical contact means 286 is covered up in FIG. 5 by themovable housing part 222 and is therefore not visible.

To reduce air turbulence in the testing compartment, an interior draftshield 265, 274 which surrounds the sample receiver 260 can be arrangedinside the testing compartment. This draft shield 265, 274 is preferablydesigned so that it conforms to the outside contour of the sample trayand/or the outside contour of the sample-heating means 270. As thesample trays being used are normally round, it suggests itself to use aninterior draft shield 265, 274 with a round contour shape. The interiordraft shield can include an upper part 274 and a lower part 265. Theupper part 274 is arranged on the movable housing part 222. The upperpart 274 of the interior draft shield encloses a cylindrical interiorspace which is open towards the sample receiver. Arranged inside thiscylindrical interior space is the sample-heating means 270. The upperpart of the interior draft shield can consist of a cylindricalcircumference wall. It is advantageous if the cylinder also has at leasta partial boundary surface above the sample receiver, preferably acylinder end wall. This surface is arranged preferably above thesample-heating means 270. Ideally, the side of the end wall that facestowards the sample-heating means 270 is heat-reflecting. Consequently, apart of the heat that is being generated is reflected by the interiordraft shield and used to heat the sample which is located on the samplereceiver 260. In addition, the end wall can have openings, so that gasescan escape into the outside atmosphere from the testing compartmentthrough the openings in the end wall and outlet vent openings 227 in thehousing 220. However, it is also possible that the end surface has noopenings.

The lower part 265 of the interior draft shield is arranged on thestationary housing part 221. The lower part 265 of the interior draftshield forms a cylindrical interior space which is open towards thesample-heating means 270. Arranged in this cylindrical interior space isthe sample receiver 260. In measuring position, the interior space ofthe upper part 274 of the interior draft shield and the interior spaceof the lower part 265 of the interior draft shield form a chamber inwhich the sample-heating means 270 and the sample receiver 260 arelocated. The upper as well as the lower part of the interior draftshield 265, 274 can be made of one piece of material or assembled fromseveral sections.

To set a sample tray in place in the testing compartment, it is possibleto use a sample tray holder 266. The sample tray holder 266 has a handle267 and seating surfaces 268 for the sample tray. During the transfer ofthe sample tray, the rim of the latter rests on the seating surfaces268. During the measurement, the sample tray rests only on the samplereceiver 260 and the sample tray holder 266 does not touch the sampletray. In particular, the weight of the sample tray holder 266 is notreceived by the weighing device.

In FIG. 6, the measuring instrument 210 of FIGS. 4 and 5 is shown inservicing position. To arrive at the servicing position, a portion ofthe movable housing part 222 has been swiveled about an essentiallyhorizontal pivot axis 225 from the loading position into the servicingposition. The sample-heating means 270 is arranged in the pivotingportion of the movable housing part 222 and is swiveled together withthe pivoting portion of the movable housing part 222 during the changeinto the servicing position. As a result, the components in the movablehousing part 222 are easily accessible for servicing. Arranged in theupper housing part 222 is the sample-heating means 270. During themeasurement process, the sample-heating means 270 is protected by aglass shield 272. Surrounding the sample-heating means 270 is the upperpart 274 of the interior draft shield.

To give a clearer view of the position and configuration of thesample-heating means 270, of the glass shield 272 and of the interiordraft shield 274, the measuring instrument 220 is shown in FIG. 7 withthe upper part 274 of the interior draft shield partially removed, andin FIG. 8 the movable housing part 222 is shown without glass shield272.

Arranged on the cylinder end surface of the interior draft shield 274 isa reflecting surface which serves to reflect the heat radiationgenerated by the sample-heating means 270. The reflection can also beachieved with a suitable reflective material of the cylinder end surfaceor a reflective coating of the cylinder end surface. An essentiallycircular light-screening barrier 273 serves to concentrate the heat raysgenerated by the sample-heating means 270.

In servicing position, the sample-heating means 270 is orientedvertically. At least a portion of the upper part 274 of the interiordraft shield is attached to the movable housing part 222 by means of aplug-in connection, wherein the plug-in direction is essentiallyvertical in the servicing position. The glass shield 272 is clampedbetween the light-screening barrier 273 and a portion of the upper part274 of the interior draft shield 274. To remove the glass shield, only apart of the interior draft shield 274 needs to be pulled out of theplug-in connection. Subsequently, the glass shield can be removed simplyby pulling it out, without using a tool. The easy removal of the glassshield 272 is of particular advantage, because it facilitates thetaking-out and cleaning of the glass shield 272 which is prone to getdirty.

The glass shield 272 and/or a portion of the upper part 274 of theinterior draft shield can be pulled out of the movable housing part in acontrolled direction by means of a guide track 275. In the servicingposition, the guide track 275 has an essentially vertical orientation.

The removal of the glass shield 272 is additionally facilitated by aservice opening 223. The service opening 223 is an access opening in themovable housing part 222 which is open only in the servicing positionbut not in the measuring position or in the loading position. Aninadvertent touching of the sample-heating means is thereby prevented,which reduces the risk of burn injuries. The service opening is realizedwith a two-part configuration of the movable housing part. According tothis concept, the two parts of the movable housing part are designed sothat in the move to the servicing position a portion of the movablehousing part does not participate in the swivel movement. Thisnon-swiveled portion clears the access to the service opening in theswiveled portion of the movable housing part.

The width of the service opening 223 is advantageously equal to orlarger than the width of the glass shield 272. This allows the glassshield to be removed easily. The service opening 223 is arranged at aright angle to the plug-in direction of the upper part of the interiordraft shield 274 and in the extension of the path of the guide track275. As a result of this arrangement, the glass shield 272 can easily bepulled out of the service opening 223.

The upper part of the interior draft shield 274 can be composed ofseveral components. Advantageously, the portion that faces towards theservice opening 223 can be removed without tools. This requires theservice opening 223 to be wider than the upper part of the interiordraft shield 274.

The sample-heating means 270 can be attached to the movable housing part222 in a variety of ways. For example, the sample-heating means 270could be fastened to the movable housing part 222 by means of screws orwith a plug-in connector. If a plug-in connector is used, thesample-heating means 270 can easily be pulled out for servicing.Ideally, this plug-in connection could be designed so that the pluginsertion is directed essentially perpendicular to the plane of theservice opening 223.

The sample-heating means 270, the light-screening barrier 273, the glassshield 272 and the upper part of the interior draft shield 274 haveopenings which, together with the outlet vent openings 227 allow thevapors and/or volatile substances escaping from a sample to be ventedinto the outside atmosphere. The openings are therefore arranged so asto ensure the direct venting of gases that escape from the sample. It isof advantage if these openings provide a direct line of vision to thesample that is located on the sample receiver 260, whereby a visualinspection of the measurement process is made possible.

In place of the interior draft shield 274 and the light-screeningbarrier 273, one could use other suitable attachment devices to hold theglass shield 272 in place.

Since the glass shield 272 is easy to take out, it can be cleaned moreeasily and quickly by the user or the service technician. Ideally, theglass shield 272 is made so that it can be cleaned in a conventionalwashing machine without damage.

The embodiments presented herein show, partially in schematic form,measuring instruments for the gravimetric determination of moisturecontent with different properties and features. For clarity's sake, thedifferent properties and features have been presented in differentexamples of embodiments, but it is also possible to realize some,several, or all of the described features and properties in one and thesame measuring instrument.

1. An instrument for gravimetrically determining moisture content of asample, comprising: a housing, comprising: a lower, stationary housingpart; and an upper, movable housing part, movable between a measuringposition and a loading position; and a weighing device, arranged insidethe housing and comprising: a load receiver, onto which the sample isplaced when the movable housing part is in the loading position in whichthe stationary housing part and movable housing part are spaced apartfrom each other; an essentially closed test compartment that surroundsthe load receiver, formed by the stationary housing part and the movablehousing part while in the measuring position; and a means for heatingthe sample, arranged in the testing compartment for heating the sampleplaced on the load receiver; and a temperature sensor, arranged tooccupy a position above the load receiver when the respective housingparts are in the measuring position and to occupy a position essentiallyto the side of the load receiver when the housing parts are in themeasuring position, the temperature sensor moving simultaneously upwardsand to the side as the sensor moves from the measuring position to theloading position.
 2. The instrument of claim 1, further comprising: arod, attached to the stationary housing part, on which the temperaturesensor is arranged.
 3. The instrument of claim 2, further comprising: afulcrum pivot that attaches the rod to the stationary housing part. 4.The instrument of claim 3, wherein: an axis of the fulcrum pivot isoriented in an essentially horizontal direction.
 5. The instrument ofclaim 2, further comprising: a spring element that, in the measuringposition, pre-tensions the rod and that uses elastic force to move therod from the measurement position to the loading position.
 6. Theinstrument of claim 5, wherein: the weight of the movable housing partprovides the force to pre-tension the spring element.
 7. The instrumentof claim 1, wherein: the sample-heating means is arranged in the movablehousing part and, in the measurement position, the temperature sensor islocated between the sample-heating means and the load receiver.
 8. Theinstrument of claim 1, further comprising: a power connection thatconnects only the stationary housing part to an electrical power source,the temperature sensor being supplied with electrical current by way ofthe stationary housing part.
 9. The instrument of claim 1, furthercomprising: a means for making and breaking an electrical contact,having a first part, solidly connected to the stationary housing part,and a second part, solidly connected to the movable housing part, suchthat: the first and second parts make an electrical contact in themeasuring position; and the first and second parts do not make anelectrical contact in the loading position
 10. The instrument of claim9, wherein: the movable housing part can be supplied with electricityonly through the means for making and breaking electrical contact. 11.The instrument of claim 1, further comprising: a means for changingposition, arranged to move the movable housing part between themeasurement position and the loading position.
 12. The instrument ofclaim 1, wherein: the movable housing part is located above thestationary housing part in the measurement position and in the loadingposition.
 13. The instrument of claim 1, wherein: the sample-heatingmeans is arranged to move in a swivel motion, with the movable housingpart, from the measurement position into the loading position.
 14. Theinstrument of claim 6, further comprising: a means for changingposition, arranged to move the movable housing part between themeasurement position and the loading position.
 15. The instrument ofclaim 6, wherein: the movable housing part is located above thestationary housing part in the measurement position and in the loadingposition.
 16. The instrument of claim 6, wherein: the sample-heatingmeans is arranged to move in a swivel motion, with the movable housingpart, from the measurement position into the loading position.